package main import ( "errors" "fmt" "reflect" sql "database/sql/driver" "gopkg.in/bluesuncorp/validator.v8" ) // User contains user information type User struct { FirstName string `validate:"required"` LastName string `validate:"required"` Age uint8 `validate:"gte=0,lte=130"` Email string `validate:"required,email"` FavouriteColor string `validate:"hexcolor|rgb|rgba"` Addresses []*Address `validate:"required,dive,required"` // a person can have a home and cottage... } // Address houses a users address information type Address struct { Street string `validate:"required"` City string `validate:"required"` Planet string `validate:"required"` Phone string `validate:"required"` } var validate *validator.Validate func main() { config := &validator.Config{TagName: "validate"} validate = validator.New(config) validateStruct() validateField() } func validateStruct() { address := &Address{ Street: "Eavesdown Docks", Planet: "Persphone", Phone: "none", } user := &User{ FirstName: "Badger", LastName: "Smith", Age: 135, Email: "Badger.Smith@gmail.com", FavouriteColor: "#000", Addresses: []*Address{address}, } // returns nil or ValidationErrors ( map[string]*FieldError ) errs := validate.Struct(user) if errs != nil { fmt.Println(errs) // output: Key: "User.Age" Error:Field validation for "Age" failed on the "lte" tag // Key: "User.Addresses[0].City" Error:Field validation for "City" failed on the "required" tag err := errs.(validator.ValidationErrors)["User.Addresses[0].City"] fmt.Println(err.Field) // output: City fmt.Println(err.Tag) // output: required fmt.Println(err.Kind) // output: string fmt.Println(err.Type) // output: string fmt.Println(err.Param) // output: fmt.Println(err.Value) // output: // from here you can create your own error messages in whatever language you wish return } // save user to database } func validateField() { myEmail := "joeybloggs.gmail.com" errs := validate.Field(myEmail, "required,email") if errs != nil { fmt.Println(errs) // output: Key: "" Error:Field validation for "" failed on the "email" tag return } // email ok, move on } var validate2 *validator.Validate type valuer struct { Name string } func (v valuer) Value() (sql.Value, error) { if v.Name == "errorme" { return nil, errors.New("some kind of error") } if v.Name == "blankme" { return "", nil } if len(v.Name) == 0 { return nil, nil } return v.Name, nil } // ValidateValuerType implements validator.CustomTypeFunc func ValidateValuerType(field reflect.Value) interface{} { if valuer, ok := field.Interface().(sql.Valuer); ok { val, err := valuer.Value() if err != nil { // handle the error how you want return nil } return val } return nil } func main2() { config := &validator.Config{TagName: "validate"} validate2 = validator.New(config) validate2.RegisterCustomTypeFunc(ValidateValuerType, (*sql.Valuer)(nil), valuer{}) validateCustomFieldType() } func validateCustomFieldType() { val := valuer{ Name: "blankme", } errs := validate2.Field(val, "required") if errs != nil { fmt.Println(errs) // output: Key: "" Error:Field validation for "" failed on the "required" tag return } // all ok }